So far, many theories are exposited such as (1) imbalance of hormones, (2) genetics, (3) circulatory failure, (4) nutrition, as the origin of androgenic alopecia.
And it has been also suggested that testosterone (androgenic hormone) played an important role on the generation of hairs.
The theory of Adachi at al in which the relation between testosterone and androgenic alopecia is proved by biochemical experiments, is as follows:
i) first, testosterone biosynthesized in testis is converted into dihydrotestosterone by 5.alpha.-reductase existed in hair follicle, sebaceous gland etc. at head. PA1 ii) dihydrotestosterone reduces the activities of adenyl cyclase remarkably. PA1 iii) it decreases cyclic-AMP in cells. PA1 iv) last, it induces lowering of energy generation of hairs and limbus and supressing of protein synthesis PA1 B.sup.a represents a bibalent group of --O--CH.sub.2 -- and PA1 R.sup.a1 represents a group of the general formula: ##STR4## (wherein R.sup.a5 and R.sup.a6 represent, independently, a hydrogen atom, halogen atom or alkyl, alkenyl or alkynyl group of from 1 to 20 carbon atom(s) which may be replaced optional carbon atom(s) of from 1 to 5 by an oxygen atom, sulfur atom, halogen atom, nitrogen atom, benzene ring, thiophene ring, naphthalene ring, carbon ring of from 4 to 7 carbon atoms, carbonyl group, carbonyloxy group, hydroxyl group, carboxyl group, azide group or nitro group) PA1 T.sup.a represents a oxygen atom, PA1 R.sup.a2 represents a hydrogen atom, PA1 R.sup.a3 represents a hydrogen atom, PA1 R.sup.a4 represents a group of --(CH2).sup.ap --COOR.sup.a8 PA1 (wherein ap represents an integer of from 1 to 10, R.sup.a8 represents a hydrogen atom or an alkyl group of from 1 to 6 carbon atom(s))] PA1 R.sup.b3 represents a chemical bond together with R.sup.b4. PA1 X.sup.b represents a halogen atom, lower alkyl group, lower alkoxy group or cyclic alkyl group, PA1 bn represents an integer of from 1 to 3, PA1 R.sup.b5 represents a hydrogen atom and PA1 Y.sup.b represents an oxyalkylene group binding benzene ring via an oxygen atom.] PA1 R.sup.c represents a hydrogen atom, PA1 R.sup.c1 represents one or two substituent(s) selected out of an alkyl, cycloalkyl, aryl, aralkyl, halogen, alkoxy, aryloxy and alkylthio group and Z.sup.c represents an oxygen atom] PA1 (R.sup.1).sub.n represents a group selected out of PA1 (ii) in case that R.sup.2 represents a hydrogen atom and R.sup.3 represents a methyl group, PA1 (R.sup.1).sub.n represents a group selected out of PA1 (i) in case that R.sup.2 represents a methyl group and PA1 R.sup.3 represents a hydrogen atom, PA1 (R.sup.1).sub.n represents a group selected out of PA1 (ii) in case that R.sup.2 represents a hydrogen atom and R.sup.3 represents a methyl group, PA1 (R.sup.1).sub.n represents a group selected out of PA1 salts of alkaline metal e.g. sodium, potassium, PA1 salts of alkaline earth metal e.g. calcium, magnesium, PA1 ammonium salts, PA1 salts of pharmaceutically acceptable amine e.g. tetramethylammonium, triethylamine, methylamine, dimethylamine, cyclopentylamine, benzylamine, phenethylamine, piperidineamine, monoethanolamine, diethanolamine, tris (hydroxymethyl)aminomethane, lysine, arginine, N-methyl-D-glucamine. PA1 (A) method using a mixed acid anhydride PA1 (B) method using an acid halide PA1 (C) method using DCC etc.
(See Biochem. Biophys. Res. Commun., 41, 884 (1970)
According to the theory it is thought that, at the results of the series of the phenomena, hairs in the growing phase shift to the resting phase, the terminal hairs change to the soft hairs, and the androgenic alopecia develops in the end.
A report by H. V. Schweikert supports this theory that large quantities of metabolites by 5.alpha.-reductase such as dihydro testosterone etc. in hair follicles of androgenic alopecia-patient exist more than that in females or healthy male. (See J. Clin. Endocr., 38, 811 (1974)
It was reported that dihydrotestosterone converted from testosterone by 5.alpha.-reductase also plays in an important physiological role in the generate of acnes (acne, pimple etc.) other than androgenic alopecia. J. B. Hay et al reported that the metabolism of testosterone by 5.alpha.-reductase was enhanced in the affected part of acne aggravated, from the study in the flux between affected skin of acne-patient and healthy skin (See Br. J. Dermatol., 91, 123 (1974)).
G. Sansone et al found that synthetic ability of dihydrotestosterone from testosterone developed from two to twenty times in the affected part of acne-patient compared to that in healthy man, they suggested that dihydrotestosterone generated by 5.alpha.-reductase greatly relates to the generation or aggravation of acne (See J. Invest. Dermatol., 56, 366 (1971)).
And, dihydrotestosterone is related to the hypertrophy of prostate. Cowan et al reported that much dihydrotestosterone existed in the prostate of prostatic hypertrophy-patient (See J. Steroid Biochemistry, 11, 609 (1979)). Recently, it was known that activity of 5.alpha.-reductase in prostate of prostatic hypertrophy-patient aggravated abnormally (See J. Clinical Endocrinol and Metabolism, 56, 139 (1983)).
From those informations it has been clear that dihydrotestosterone plays an important role in the generation and development of prostatic hypertrophy.